IUCr journals

Convergent-beam neutron crystallography

J. Appl. Cryst. (2004). 37, 778–785 [doi:10.1107/S0021889804015882]

[intensity gains] Intensity gains with the optic for the three lowest-order nickel powder diffraction peaks in detector banks at three different scattering angles as a function of neutron wavelength.
Focusing polycapillary optics enhance diffraction intensities for neutron convergent beam time-of-flight crystallography with a broad wavelength bandwidth. An optic with focal distance of 15 mm and beam convergence of ~15° has a focal spot width of 100 μm for 3.2 Å neutrons. For an MnF2 single-crystal sample as small as 0.01 mm3, we observe an expected intensity gain of ~100 for a 020 Bragg peak. Measurements on a powder diffractometer show diffracted beam intensities for Ni powder with expected gains in excess of 500 for samples of this diameter. Backscattering geometry minimizes degradation of resolution for this large beam convergence.

W. M. Gibson, A. J. Schultz, J. W. Richardson, J. M. Carpenter, D. F. R. Mildner, H. H. Chen-Mayer, M. E. Miller, E. R. Maxey and R. Youngman